Scrub brush



FIG. 1 is a front right side perspective view of a scrub brush which embodies our design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view, the left side view being a mirror image thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken line showing of bristles illustrates environmental structure which forms no part of the claimed design. 

The ornamental design for a scrub brush, as shown and described. 